U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Day Three

acus01 kwns 180046 
Storm Prediction Center ac 180044 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0744 PM CDT Wednesday Sep 17 2014 

Valid 180100z - 181200z 

..no severe thunderstorm areas forecast... 

isolated strong storms will continue over parts of the central Great 
Plains and along the Oklahoma/Arkansas border this evening. 

Small mesoscale convective system that evolved over the Ozark Plateau has progressed south-southwestward 
into far northestern OK and northwestern Arkansas. Leading edge of this activity is 
propagating at roughly 15-20kt and may produce locally strong winds. 
Latest wdssii mesh data suggests marginally severe hail remains with 
the strongest updrafts over eastern Crawford County Arkansas. However...hail 
should gradually wane in intensity with loss of heating. 

Farther northwest...a few strong thunderstorms persist across the High 
Plains of northestern Colorado into northwestern Kansas. This convection should gradually 
spread/develop southeastward within favorable southeasterly low-level inflow...though 
activity should remain isolated. Gusty winds and perhaps marginally 
severe hail are the primary threats for the next few hours. 

Tropical remnants of Odile have progressed inland across northwestern Mexico 
and are spreading over southeastern Arizona/southern nm and far West Texas. While lapse 
rates are poor with this system 00z sounding from epz suggests 
sufficient buoyancy/shear for organized multi-cell updrafts. 
Another pronounced middle-level feature is advecting across the Texas 
Panhandle. Long radar loops clearly show a weakening circulation 
just west of Ama and this feature may be enhancing strong convection 
across the Texas South Plains. Multiple storm mergers/outflow suggest 
this cluster will propagate toward I-20 before weakening. 

.Darrow.. 09/18/2014 

Mesoscale Discussion

acus11 kwns 180046 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 180046 

Mesoscale discussion 1727 
National Weather Service Storm Prediction Center Norman OK 
0746 PM CDT Wednesday Sep 17 2014 

Areas affected...parts of western Arkansas and adjacent eastern OK 

Concerning...severe potential...watch unlikely 

Valid 180046z - 180245z 

Probability of watch issuance...5 percent 

Summary...low-end severe risk may linger locally another 1-2 hours 
across parts of the western Arkansas vicinity. 

Discussion...latest radar loop shows a cluster of thunderstorms 
moving southward/southwestward in vicinity of the northwestern Arkansas/eastern OK border at this time...near and just 
to the cool side of an associated outflow boundary. Evening radiosonde observations 
confirm that a moderately unstable airmass exists across this 
area...as has been depicted by objective analyses...thus assisting 
in continued cell regeneration along the outflow boundary. 

The strongest storm -- now moving southward across Crawford Colorado -- had 
shown supercell characteristics over the past couple of hours...but 
has recently weakened. While shear over southern MO/northern Arkansas is supportive 
of updraft rotation...flow aloft weakens with southwestward extent -- and 
thus expect a gradual/continued decrease in severe risk as storms 
slowly move away from the more favorably sheared environment. That 
said however...degree of cape supports a continuation of 
storms...and thus severe risk may linger for the next 1-2 hours as 
storms continue advancing across the OK/Arkansas border area. 

.Goss/Edwards.. 09/18/2014 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 36529510 36289495 35879434 35409353 34729336 34539443 
35379567 36469559 36529510